1343332 - Rule view seems confused about what's actually applied

Status: NEW

(DevTools :: Inspector: Rules, defect, P3)

Description

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Sorry for the elaborate STR, I'm not sure yet what's important about this case and what is not...

STR:

1. Download an RTL build of Firefox
  * The "Force RTL" add-on is not enough here, you seem to need an actual RTL build
2. Start up the RTL build
  * You may want to use a separate profile
3. Open the Browser Toolbox
4. In the Inspector, search for the element #urlbar-wrapper
  * You should see the state as shown in "Initial Rule View" screenshot
5. From the Rule View state, it appears that `margin-inline-start` is set to 0
6. In the `window:not([chromehidden~="toolbar"]) #urlbar-wrapper:-moz-locale-dir(rtl)` rule set, disable `transform: scaleX(-1)`
7. Add a new rule `margin-inline-start: 0` to the rule set where `transform` was just disabled
  * Adding this rule makes a gap between the location bar and back / forward control go away

ER:

The added `margin-inline-start: 0` should have no effect, since it repeats the already applied value from a different rule set. 

AR:

The added / redundant rule `margin-inline-start: 0` definitely has some effect, because the styling changes when toggling it on and off (even though a different rule set contains exactly the same rule).

Comment 1

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Attachment: Initial Rule View.png

Comment 2

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Attachment: Final Rule View.png

Comment 3

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

Here's an example RTL build (he locale):

https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central-l10n/firefox-54.0a1.he.mac.dmg

Comment 4

[Patrick Brosset <:pbro>]

P3 for now, because of the complex STRs, it might be possible to reproduce in a more isolated use case, but I was not able to so. I ll spend some time on this. P3 for now.
Inspector bug triage (filter on CLIMBING SHOES).

Comment 5

[J. Ryan Stinnett [:jryans] (Use needinfo, replies may be slow)]

:tromey suggested it could be a platform issue with how the rules are applied.

I hit this STR while working on bug 1340206, which is now fixed, so it's possible the changed landed there are hiding the issue.

Here's a better link to an RTL build before changes in bug 1340206:

https://archive.mozilla.org/pub/firefox/nightly/2017/03/2017-03-01-03-02-02-mozilla-central-l10n/firefox-54.0a1.he.mac.dmg

Comment 6

[Patrick Brosset <:pbro>]

(In reply to J. Ryan Stinnett [:jryans] (use ni?) from comment #5)
> :tromey suggested it could be a platform issue with how the rules are
> applied.
That was my gut feeling too. I tried doing the same changes from the style-editor and ran into the same bug.
If this is a platform issue, we'll need to provide an isolated test case, so I'll keep my needinfo for now.

Comment 7

[Patrick Brosset <:pbro>]

Sorry, but at this stage, it's probably useless for me to keep the ni? flag ...